The first experiment examining the target position of regressive saccades during reading was conducted by Frazier and Rayner and dates back to the 1980s (Frazier & Rayner, 1982). Frazier and Rayner assumed that eye movements are directly driven by linguistic processes and that the decision when and where to regress is under strict linguistic con- trol. Accordingly, eye movements should provide an insight into the parsers reanalysis processes during sentence comprehension.
Based on the finding that garden path sentences lead to an increased probability of regressions out of the disambiguating region, Frazier and Rayner proposed three dif- ferent opportunities how the parser could deal with these processing difficulties: a) The parser reads the entire sentence again (forward reanalysis hypothesis), b) The parser
29 systematically proceeds backward and tries out alternatives (backward reanalysis hy- pothesis), c) The parser regresses to a position where he expects the source of the error (selective reanalysis hypothesis).
In their experiment, Frazier and Rayner let participants read English garden path sentences like (3) while the participants’ eyes were monitored.
(3) Since Jay always jogs a mile and a half seems like a very short distance to him. An inspection of the regression proportions revealed that 51% of all regressions in gar- den path sentences were initiated from the disambiguating region (seems) where the initially preferred sentence interpretation turned out to be wrong. In addition, 53% of all regressions initiated in the disambiguating region and beyond ended in the ambigu- ous region (a mile and a half) which indicates that the eyes were directly moved to the point where the erroneous analysis was developed. These findings support the selective reanalysis hypothesis that predicts that the parser regresses to the region where he ex- pects the source of the error.
Nonetheless, Frazier and Rayner also found evidence that although regressions provide a typical strategy in order to deal with comprehension difficulties, readers do not always regress when faced with garden path sentences. Rather, in some cases com- prehension difficulties just increased fixation durations. This finding has not been dis- cussed by the authors in more detail but points to the opportunity that reanalysis might be covert, i.e., without triggering a regressive eye movement. In addition, this suggests that the availability of information that is needed to solve processing problems might depend on individual memory capacities or different sentence material (see also Lewis, 1998).
However, two further results of the study have to be mentioned with regard to the selective reanalysis hypothesis. First, Frazier und Rayner pointed out that beyond the dominant pattern of selective reanalysis, there was an increased probability of re- gressions initiated from the very end of the sentence and targeting the sentence begin- ning. Thus, the readers reread the entire sentence after finishing it for the first time. These sometimes called “sentence wrap-up” effects occur frequently in reading, as dis- cussed earlier, but they question the general validity of the selective reanalysis hypoth- esis. Thus, Frazier and Rayner conclude that “it is not obvious how regressions to the be-
30 The second point also addresses the general validity of the selective reanalysis hypothesis. The results show that although selective reanalysis seems to be the domi- nant pattern for the target selection of regressions, the regressions nonetheless show a relatively high variance with regard to their landing sites. Thus, if the selective reanalysis hypothesis is indeed the leading principle of regressive eye movements, then this ac- count also has to explain why so many regressions obviously fail to reach their intended target position.
The selective reanalysis hypothesis is further questioned by the fact that the am- biguous region in the sentences was directly followed by the disambiguation region. Thus, the possibility cannot be ruled out that the eyes in certain cases just by default regressed to the word directly to the left of the currently fixated word because it is the “smallest possible regression” (Mitchell, Shen, Green, & Hodgson, 2008), independently of whether this word contained the source of the error or not.
The major limitation of Frazier and Rayner’s experiment, however, was the lack of sta- tistical evidence due to the overall small number of regressions. Thus, twenty years after Frazier and Rayner’s famous experiment, Meseguer, Carreiras and Clifton further exam- ined the selective reanalysis hypothesis, using locally ambiguous sentences in Spanish (Meseguer, Carreiras, & Clifton, 2002).
In the experiment, forty-four native speakers of Spanish were asked to read sen- tences like (4) while their eyes were tracked.
(4) El professor dijo que los alumnos
se levantaran del asiento cuando los directores entraron / entraran en la clase. [The teacher said that the students
had to stand up from their seats when the directors came / come into the room] In these sentences, the verb entraron / entraran disambiguates the ambiguous adverb cuando to be either high attached to the matrix verb dijo (in the case of entraron) or to be low attached to the second verbal phrase se levantaran (in the case of entraran). The results revealed a preference for the low VP2 attachment, indicated by increased second pass reading times and a higher probability of regressions for the VP1 attached sen- tences in the post-disambiguation region. In addition, statistical analysis provided sig- nificant differences between the two sentence types with regard to the target position of regressions: Regressive eye movements that were initiated in the post-disambiguation
31 region targeted more frequently the matrix verb dijo and the adverb cuando in the sen- tences with VP1 attachment than in sentences with VP2 attachment. Hence, the authors interpreted their findings as additional evidence for the selective reanalysis hypothesis. But although the results are generally in line with the findings of Frazier and Rayner, they raise some further questions and problems. The first problem is a method- ological issue and refers to the sentence structure. As mentioned earlier, there is a gen- eral tendency to regress from the end of a sentence, independently of comprehension difficulties. The results of Frazier and Rayner show that these end-of-sentence regres- sions have to be functionally dissociated from regressions initiated in order to revise a misleading analysis of the linguistic material because the former tend to target the be- ginning of the sentence instead of a specific error source. In Meseguer at al.’s experiment, however, the sentence’s final region coincided with the post-disambiguating region, so that end-of-sentence regressions can hardly be distinguished from regressions due to reanalysis (see also Mitchell et al., 2008, for a discussion).
The second issue refers to the first pass reading times in the disambiguation and post-disambiguation region. Whereas Frazier and Rayner reported increased fixation durations on the sentence region where the wrong analysis became apparent, Meseguer and colleagues found no differences between the two sentence types with regard to fix- ation durations in the disambiguation and post-disambiguation region. They interpreted this lack of an effect as a hint that the participants did not reanalyze the sentence covertly (i.e., without triggering a regressive eye movement). But together with the possible end- of-sentence regressions, this raises the question if all participants were equally garden pathed and if in fact all participants reanalyzed the sentence. In addition, the compre- hension questions did not probe the attachment side of the sentences, so that it remains open with which sentence interpretation the participants finally came up with.
The third question addresses the reanalysis itself. Although Meseguer and col- leagues provided a detailed description of how a sentence like (4) has to be reanalyzed in order to get the intended interpretation (i.e., attaching the adverb cuando to the ma- trix verb dijo instead of the second verb phrase se levantaran), they did not propose a clear hypothesis how this reanalysis is carried out. In other words, they did not specify the exact information (i.e., the portion of the sentence) that is needed in order to reana- lyze the sentence. Remarkably, the results showed not only one but two preferred target regions: The matrix verb dijo and the adverb cuando. Meseguer and colleagues discussed
32 this finding in their paper but were not able to give a satisfying answer. From the per- spective of the selective reanalysis hypothesis, however, this raises the question to what extent a linguistically motivated single target region for regressions can be defined, even if the underlying language processing mechanisms are well studied.
In sum, although both experiments provide some support for the assumption that regressions are under linguistic control and are directed to the portion of the sen- tence where the parser expects the source for the error, they both suffer from methodo- logical as well as interpretive problems. Particularly, the selective reanalysis hypothesis is restricted to regressions caused by comprehension difficulties in garden path sen- tences and therefore cannot account for all kinds of regressive eye movements. Thus, some doubts remain that regressions and their target positions are indeed driven by lin- guistic factors.